Hi Jonathan,
I am also in the Woodbusiness and my set-up is as follows:
Firstly I focus on the main category pages: www.company.com/categoryA etc..
Than I made for every wood specie pages aswell: company.com/woodA etc.. This generates good traffic from people who are looking for specific products in a specific type of wood
Now I am mainly focussing on product pages for my experience is that how more specific the traffic is the better the conversion rates become:
company.com/category1/woodA-productA-size
My product names all begin with the sort of wood than the product (door, table, etc...) and last the exact measurements.
This works better for me than the subcategories.
Hope it helps. Good luck!
Tymen